某难选氧化铁矿磁化焙烧流程优化研究与应用

酒钢镜铁山铁矿石原块矿焙烧分选工艺中，存在一次干选尾矿围岩含量较高的问题，不仅二次焙烧量大、能耗高、焙烧质量欠佳，而且影响二次干选效果。为解决这些问题，对一次干选尾矿进行了扫选工艺技术研究。结果表明，对一次干选尾矿进行再选，粗粒级矿石使用分选机分选，细粒级使用干式磁选机分选，扫选精矿与原矿合并进行一次焙烧，不仅取消了二次焙烧作业，而且减少了返回焙烧矿量，降低了焙烧工艺能源消耗，减少了金属流失。     

Role of composition and grain size in controlling the structure sensitive magnetic properties of Sm~(3+) substituted nanocrystalline Co-Zn ferrites

The nanocrystalline samarium substituted Co-Zn ferrites with chemical formula Co_(0.7)Zn_(0.3)SmyFe_(2-y)O_4(where y=0,0.01,0.02,0.03,0.04) were synthesized by sol-gel autocombustion route.The analysis of Xray diffractograms(XRD) reveals the formation of cubic spinel structure.The planes indexed from XRD analyses were confirmed in the selected area electron diffraction(SAED) image of the sample.Nanocrystalline nature of the particles in the ferrite samples was confirmed by TEM.The morphology was analyzed by scanning electron microscopy(SEM).Magnetic measurements show an increase in the magnetization for x ≤0.03.The decrease in magnetization due to spin canting is observed for x=0.04.The coercivity depends on Sm~(3+)doping concentration,grain size and saturation magnetization.The complex permeability of the ferrites was analyzed as the function of frequency and Sm~(3+)composition(y).The real part of complex permeability varies linearly with the grain size.     

国外某褐铁矿石磁化焙烧—磨矿—弱磁选试验

国外某褐铁矿石铁品位为54.12%,褐铁矿多呈疏松、多孔的胶状分布,少部分呈块状或鲕状分布。采用单一浮选和重选工艺不能获得合格铁精矿。为给该矿石开发利用提供依据,进行了磁化焙烧—磨矿—磁选试验,考察了焙烧温度、焙烧时间、烟煤用量、磨矿细度、磁场强度对精矿指标的影响。结果表明:在烟煤用量为15%、焙烧温度为850℃、焙烧时间为60 min,焙烧产品自然冷却后经球磨磨细至-0.074 mm占90%,在磁场强度为160 k A/m条件下弱磁选,可获得铁品位为64.65%、回收率为86.05%的精矿。     

Role of BaO/SrO layers in deciding the electronic structure of Cu0.3Co0.7Ba2−xSrxYCu2O7+δ (CoCu-1212) x = 0, 1 and 2

In this paper we report the change in electronic structure of Cu_0.3Co_0.7Ba_2−xSr_xYCu₂O_7+δ with change in structural pressure. Rietveld refined X-ray diffraction (XRD) pattern shows that the samples are phase pure. Decrease in lattice parameters with increasing x, confirms replacement by Sr ion at Ba ion site. The calculated tolerance factor of the systems is in accord with lattice parameter changes. The X-ray photoelectron spectroscopy (XPS) is made to find out the variation in ionic state of Co and Cu with ionic size variation in BaO/SrO layers. Effect of the same on the electronic structure and transport properties is explored. The XPS measurement reveals that Cu is in mixed 1+/2+ state and variation in valence state is non-monotonous with increasing x. Whereas Co is in mixed 3+/4+ state and with increasing x its valence state is increasing. The observed changes in electronic structure are subject of structural changes. The resistivity measurement shows that normal state conductivity decreases with increasing x. Resistivity behaviour indicates about holes in Cu/CoO_x planes taking part in charge transport. The magnetic measurement (M-T and M-H) shows that paramagnetic nature for all the compositions. The presence of Cu ions in Cu/CoO_x chains/planes results in paramagnetic behaviour.     

Effects of Nd:YAG laser irradiation on structural and magnetic properties of Li0.5Fe2.5O4

In the present paper we report our results on the effect of Nd:YAG laser irradiation on the structural and magnetic properties of Li_0.5Fe_2.5O₄ spinel ferrite prepared by solid-state reaction technique. X-ray diffraction analysis was carried out to confirm the formation of the single phase cubic spinel structure. The lattice constant calculated from X-ray diffraction data (XRD) goes on increasing with non irradiated phase to exceeding higher doses of irradiation. The distribution of the substituted ions over the different lattice sites is determined from XRD and infrared spectra. The damage structure and morphological investigations were carried out by using scanning electron microscopy and transmission electron microscopy techniques. It has been observed from our data on magnetic properties that laser irradiation severely affects the magnetization. From the magnetization measurements it has been observed that the saturation magnetization decreases with increase in the laser dose rate. The observed reduction in the saturation magnetization after irradiation is understood on the basis of the partial formation of paramagnetic centers and rearrangement of cations in the lattice.     

Structural and magnetic properties of La0.85Ca0.15Mn1 − xCrxO3

Chromium (Cr) is doped at the Mn site of La_0.85Ca_0.15MnO₃ system to explore its complex ferromagnetic insulating (FMI) state. The Rietveld refinement of neutron diffraction data indicates that there is no structural change owing to Cr substitution in La_0.85Ca_0.15Mn_1 − xCr_xO₃ (0 ≤ x ≤ 0.1). Nevertheless, it strengthens the magnetic couplings and the system shifts towards enhanced ferromagnetic (FM) ordering. Doping with Cr is found to stabilise the FMI state at low temperatures. The magnetic moment of the parent compound (for x = 0) obtained from neutron diffraction data recorded at low temperature (17 K) is found to be ~ 3.53(5) μ_B and is close to the theoretically estimated value of 3.85 μ_B. This value is higher than previously reported value of 2.90 μ_B.     

(Bi13Co11)Co2O40–Co3O4 nanocomposites: Synthesis,characterization and application as substrate for microstrip patch antenna

The sillenite-cobaltite nanocomposites with chemical formula (Bi₁₃Co₁₁)Co₂O₄₀–Co₃O₄ were synthetized and characterized for application as substrate in a microstrip patch antenna. To prepare the sample, the combustion method using urea as fuel was applied. The structural and vibrational characterizations were done through X-ray diffraction and infrared spectroscopy. The morphology of the sample was studied through FESEM images. The magnetization as a function of magnetic field recorded at 300 K confirmed the paramagnetic character of the sample. Electric characterization was performed from 1.0 GHz to 8.5 GHz aiming a wide frequency spectrum data, presenting steady real relative permittivity around 7, with low losses as results. A microstrip patch antenna was designed by cavity method with the nanocomposite as substrate for application in X-band communication services. Reflection coefficient measurements displayed a good agreement with simulations, achieving only 0.39% error in resonance frequency, validating the performed morphological and electrical characterizations, as antenna design. Simulated radiation pattern is also presented, with coherent results for a directive device.     

Magnetization processes in submicronic Co dots studied by means of micromagnetic calculations

The magnetization nucleation mechanisms taking place in “perfect” submicronic cobalt dots obtained by means of three-dimensional micromagnetic simulations are shown. Attention is focused on the study of the transition from parallel-to-plane to perpendicular-to-plane magnetization occurring as the thickness of the dot is increased. Simulations show different nucleation and magnetization reversal mechanisms as thickness varies. For a 35 nm dot, nucleation of stripe domains takes place. Stripe domains evolve with the decrease of the in-plane applied field towards a configuration of “bended stripe” domains as a result of the need for a lateral flux closure. The same nucleation mechanism has been found for thicker dots and is responsible for the appearance of diagonal domains for high thicknesses. For 25 nm thick dots no stripe domains are present and a full in-plane magnetization configuration has been obtained for which flux closure takes place with the formation of two distorted vortices at both sides of the dot.     

Multiple Magnetic Ordering Temperatures in RuSr<Subscript>2</Subscript>Eu<Subscript>1.5</Subscript>Ce<Subscript>0.5</Subscript>Cu<Subscript>2</Subscript>O<Subscript>10−<Emphasis Type="Italic">δ</Emphasis></Subscript> System

We report synthesis and magnetic characterization of variously processed magneto-superconducting (Rutheno-cuprates) RuSr₂Eu_1.5Ce_0.5Cu₂O_10−δ . The compound crystallizes in I4/mmm tetragonal structure. Magnetization measurements showed bulk magnetic ordering and superconductivity at around 100 K and 30 K, respectively. Further, the careful examination of the low field magnetic susceptibility reveals two minor magnetic transitions at around 135 K and 200 K, in addition to the major transition at 100 K. When the samples are processed in different environments of air, O₂ and slightly pressurized O₂, the nature of magnetic transitions and the superconductivity changes dramatically. The highest superconducting transition is achieved for the high pressure O₂ annealed samples and the lowest for the air annealed one. On the other hand, the minor magnetic transitions are more prominent in air-annealed samples. Though the minor magnetic transitions are intrinsic to all variously processed samples, they are not clearly seen for higher O₂ content samples. Basically, the Ru spins order antiferro magnetically at around 200 K (first minor transition), and reorients themselves at 125 K (second minor transition) before finally ordering in canted ferromagnetic state or a spin glass structure. These results can be explained on the basis of fluctuating valance of Ru⁴⁺/Ru⁵⁺.